Changes In Muscle Architecture Research Articles

Passive and dynamic muscle architecture during transverse loading for gastrocnemius medialis in man

External forces from our environment impose transverse loads on our muscles. Studies in rats have shown that transverse loads result in a decrease in the longitudinal muscle force. Changes in muscle architecture during contraction may contribute to the observed force decrease. The aim of this study was to quantify changes in pennation angle, fascicle dimensions, and muscle thickness during contraction under external transverse load.Electrical stimuli were elicited to evoke maximal force twitches in the right calf muscles of humans. Trials were conducted with transverse loads of 2, 4.5, and 10 kg. An ultrasound probe was placed on the medial gastrocnemius in line with the transverse load to quantify muscle characteristics during muscle twitches.Maximum twitch force decreased with increased transverse muscle loading. The 2, 4.5, and 10 kg of transverse load showed a 9, 13, and 16% decrease in longitudinal force, respectively. Within the field of view of the ultrasound images, and thus directly beneath the external load, loading of the muscle resulted in a decrease in the muscle thickness and pennation angle, with higher loads causing greater decreases. During twitches the muscle transiently increased in thickness and pennation angle, as did fascicle thickness. Higher transverse loads showed a reduced increase in muscle thickness. Smaller increases in pennation angle and fascicle thickness strain also occurred with higher transverse loads.This study shows that increased transverse loading caused a decrease in ankle moment, muscle thickness, and pennation angle, as well as transverse deformation of the fascicles.

Tensiomyography detects early hallmarks of bed-rest-induced atrophy before changes in muscle architecture.

In young and older people, skeletal muscle mass is reduced after as little as 7 days of disuse. The declines in muscle mass after such short periods are of high clinical relevance, particularly in older people who show a higher atrophy rate and a slower or even a complete lack of muscle mass recovery after disuse. Ten men (24.3 yr; SD 2.6) underwent 35 days of 6° head-down tilt bed rest, followed by 30 days of recovery. During bed rest, a neutral energy balance was maintained, with three weekly passive physiotherapy sessions to minimize muscle soreness and joint stiffness. All measurements were performed in a hospital at days 1-10, 16, 28, and 35 of bed rest (BR1-BR10, BR16, BR28, and BR35, respectively) and days 1, 3, and 30 after reambulation (R + 1, R + 3, and R + 30, respectively). Vastus medialis obliquus (VMO), vastus medialis longus (VML), and biceps femoris (BF) thickness (d) and pennation angle (Θ) were assessed by ultrasonography, whereas twitch muscle belly displacement (Dm) and contraction time (Tc) were assessed with tensiomyography (TMG). After bed rest, d and Θ decreased by 13-17% in all muscles ( P < 0.001) and had recovered at R + 30. Dm was increased by 42.3-84.4% ( P < 0.001) at BR35 and preceded the decrease in d by 7, 5, and 3 days in VMO, VML, and BF, respectively. Tc increased only in BF (32.1%; P < 0.001) and was not recovered at R + 30. TMG can detect early bed-rest-induced changes in muscle with higher sensitivity before overt architectural changes, and atrophy can be detected. NEW & NOTEWORTHY Detection of early atrophic processes and irreversible adaptation to disuse are of high clinical relevance. With the use of tensiomyography (TMG), we detected early atrophic processes before overt architectural changes, and atrophy can be detected using imaging technique. Furthermore, TMG detected irreversible changes of biceps femoris contraction time.

Impact of transversal calf muscle loading on plantarflexion

Muscle compression commonly occurs in daily life (for instance wearing backpacks or compression garments, and during sitting). However, the effects of the compression on contraction dynamics in humans are not well examined. The aim of the study was to quantify the alterations of contraction dynamics and muscle architecture in human muscle with external transverse loads.The posterior tibialis nerve of 29 subjects was stimulated to obtain the maximal double-twitch force of the gastrocnemius muscle with and without transverse compression that was generated using an indentor. The muscle architecture was determined by a sonographic probe that was embedded within the indentor. Five stimulations each were conducted at 5 conditions: (1) pretest (unloaded), (2) indentor loading with 2 kg, (3) 4.5 kg, (4) 10 kg, and (5) posttest (unloaded).Compared to the pretest maximal force decreased by 9%, 13% and 16% for 2 kg, 4.5 kg and 10 kg, respectively. The half-relaxation time increased with increased transverse load whereas the rate of force development decreased from pretest to 2 kg and from 4.5 kg to 10 kg. The lifting height of the indentor increased with transverse load from 2 kg to 4.5 kg but decreased from 4.5 kg to 10 kg. Increases in pennation during the twitches were reduced at the highest transverse load.The results demonstrate changes of the contraction dynamics due to transversal muscle loading. Those alterations are associated with the applied pressure, changes in muscle architecture and partitioning of muscle force in transversal and longitudinal direction.

Diffusion tensor imaging and diffusion modeling: Application to monitoring changes in the medial gastrocnemius in disuse atrophy induced by unilateral limb suspension.

Diffusion tensor imaging (DTI) assesses underlying tissue microstructure, and has been applied to studying skeletal muscle. Unloading of the lower leg causes decreases in muscle force, mass, and muscle protein synthesis as well as changes in muscle architecture. To monitor the change in DTI indices in the medial gastrocnemius (MG) after 4-week unilateral limb suspension (ULLS) and to explore the feasibility of extracting tissue microstructural parameters based on a two-compartment diffusion model. Prospective cohort study. Seven moderately active subjects (29.1 ± 5.7 years). 3T, single-shot fat-suppressed echo planar spin echo sequence. Suspension-related changes in the DTI indices (eigenvalues: λ1 , λ2 , λ3 , fractional anisotropy; coefficient of planarity) were statistically analyzed. Changes in model-derived tissue parameters (muscle fiber circularity and diameter, intracellular volume fraction, and residence time) after suspension are qualitatively discussed. Changes in the DTI indices of the MG between pre- and postsuspension were assessed using repeated-measures two-way analysis of variance (ANOVA). All the eigenvalues (λ1 : P = 0.025, λ2 : P = 0.035, λ3 : P = 0.049) as well as anisotropic diffusion coefficient (P = 0.029) were significantly smaller post-ULLS. Diffusion modeling revealed that fibers were more circular (circularity index increased from 0.55 to 0.95) with a smaller diameter (diameter decreased from 82-60 μm) postsuspension. We have shown that DTI indices change with disuse and modeling can relate these voxel level changes to changes in the tissue microarchitecture. 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.

Quantitative muscle MRI and ultrasound for facioscapulohumeral muscular dystrophy: complementary imaging biomarkers

ObjectiveTo assess the overlap of and differences between quantitative muscle MRI and ultrasound in characterizing structural changes in leg muscles of facioscapulohumeral muscular dystrophy (FSHD) patients.MethodsWe performed quantitative MRI and quantitative ultrasound of ten leg muscles in 27 FSHD patients and assessed images, both quantitatively and visually, for fatty infiltration, fibrosis and edema.ResultsThe MRI fat fraction and ultrasound echogenicity z-score correlated strongly (CC 0.865, p < 0.05) and both correlated with clinical severity (MRI CC 0.828, ultrasound CC 0.767, p < 0.001). Ultrasound detected changes in muscle architecture in muscles that looked normal on MRI. MRI was better in detecting late stages of fatty infiltration and was more suitable to assess muscle edema. Correlations between quantitative and semi-quantitative scores were strong for MRI (CC 0.844–0.982, p < 0.05), and varied for ultrasound (CC 0.427–0.809, p = 0.026–p < 0.001).ConclusionsQuantitative muscle MRI and ultrasound are both promising imaging biomarkers for differentiating between degrees of structural muscle changes. As ultrasound is more sensitive to detect subtle structural changes and MRI is more accurate in end stage muscles and detecting edema, the techniques are complementary. Hence, the choice for a particular technique should be considered in light of the trial design.

Functional deficits may be explained by plantarflexor remodeling following Achilles tendon rupture repair: Preliminary findings

Achilles tendon ruptures are common injuries that often lead to long-term functional deficits. Despite the prevalence of these injuries, the mechanism responsible for limited function has not yet been established. Therefore, the purpose of this study was to present preliminary findings that support a hypothesis that skeletal muscle remodeling is the driving factor of poor outcomes in some patients. Biomechanical and ultrasonography assessments were performed on a patient that presented with poor functional outcomes 2.5 years after a surgically-repaired acute Achilles tendon rupture. Single-leg heel raise height was decreased by 75% in the affected limb (3.0 cm compared to 11.9 cm) while walking mechanics showed no deficits. Ultrasonography revealed that the affected medial gastrocnemius muscle was less thick and had shorter, more pennate fascicles compared to the unaffected limb. A simple computational model of a maximal-effort plantarflexion contraction was employed to test the implications of changes in muscle architecture on single-leg heel raise function. Subject-specific measurements of fascicle length and pennation were input into the model, which supported these architectural parameters as being drivers of heel raise function. These preliminary findings support the hypothesis that an Achilles tendon rupture elicits changes in skeletal muscle architecture, which reduces the amount of work and power the joint can generate. This multidisciplinary framework of biomechanical, imaging, and computational modeling provides a unique platform for studying the complex interactions between structure and function in patients recovering from Achilles tendon injuries.

Sex-Related Responses to Eccentric-Only Resistance Training in Knee-Extensors Muscle Strength and Architecture

ABSTRACTPurpose: The present study aimed to investigate whether or not eccentric-only training induced different sex-related adaptations in vastus lateralis muscle architecture and knee extensors strength. Methods: Thirteen healthy women and 13 healthy men were recruited. Vastus lateralis pennation angle, fascicle length, and muscle thickness, as well as knee extensors eccentric, isometric, and concentric peak torque and one-repetition maximum (1RM) were measured. Both women and men underwent a unilateral iso-load knee-extension eccentric-only training with 120% of the concentric 1RM, consisting of 4 sets × 10 repetitions twice a week for a total of 8 weeks. Results: Pennation angle increased in women (+ 14%, 95% CI [10, 17], effect size [ES] = 1.54) but not in men (+ 5%, 95% CI [−1, 11], ES = 0.28), while fascicle length increased in both women (+ 7%, 95% CI [4, 10], ES = 1.02) and men (+ 12%, 95% CI [8, 16], ES = 1.82) and muscle thickness increased in women (+ 13%, 95% CI [8, 18], ES = 1.11) and men (+ 11%, 95% CI [7, 15], ES = 0.89). In both women and men, eccentric (18%, 95% CI [11, 25], ES = 0.96, and 16%, 95% CI [9, 22], ES = 0.82, respectively), isometric (17%, 95% CI [11, 23], ES = 0.53, and 17%, 95% CI [10, 24], ES = 0.62), concentric (12%, 95% CI [7, 16], ES = 0.49, and 9%, 95% CI [5, 13], ES = 0.42) peak torque and 1RM (10%, 95% CI [6, 14], ES = 0.53, and 10%, 95% CI [5, 15], ES = 0.50) similarly increased after the intervention. Conclusions: This study showed that the adaptations in strength are not sex-dependent, but the increases in pennation angle only in women suggest that the changes in muscle architecture may depend on sex.

Structural Determinants of Muscle Gearing During Dynamic Contractions.

In skeletal muscle, interactions between contractile and connective tissue elements at multiple scales result in emergent properties that determine mechanical performance. One of these phenomena is architectural gearing, which is quantified as the ratio of muscle velocity to muscle fiber velocity. Many pennate muscles operate with a gear ratio greater than one because muscles shorten through a combination of muscle fiber shortening and fiber rotation. Within a muscle, gearing is variable across contractions. During low force contractions, muscles operate at high gear while muscles operate at low gear during high force contractions. This variable gearing has a significant impact on muscle performance as muscle architectural changes favor muscle speed during fast contractions and muscle force during slow, high force contractions. We hypothesize that gearing in any given contraction is determined by the dynamic interaction of fiber-generated forces, fluid force transmission, and the elastic behavior of intramuscular connective tissues. Because muscle is isovolumetric, muscle fibers must bulge radially when they shorten. Radial bulging and fiber-generated forces off-axis from the muscle line of action exert forces that load connective tissues that ensheath fibers, fascicles, and the whole muscle. The way in which fluid pressures and fiber forces interact to load connective tissues in three-dimensions remains poorly understood because of the complex and multiscale nature of these interactions. Here we review evidence for variable gearing in pennate muscles, present a conceptual model that describes the fundamental interactions that determine gearing, and discuss where gaps remain in our understanding of the determinants and consequences of muscle shape change and variable gearing.

Effects of Instrument Assisted Soft Tissue Mobilization on Biceps Femoris Muscle Architecture

Instrument assisted soft tissue mobilization (IASTM) is a popular therapeutic modality that is often used to treat skeletal muscle restriction and injury. The efficacy and mechanism by which IASTM elicits a therapeutic effect is not fully understood. This study was designed to explore if any reported benefits of IASTM stem from changes in skeletal muscle architecture. PURPOSE: Examine the effects of IASTM on biceps femoris (BF) ultrasonography (US) baseline measurements of cross sectional area (CSA) and echo intensity (EI) as well as pennation angle (PA) at three different joint positions. Joint positions included 90°, mid- (MidROM), and end-range of motion (ROM) (EndROM). METHODS: Seventeen female participants (mean±SD: age=21.12±0.78 years) participated in this study. Participants were placed in a prone position for the IASTM treatment and for CSA and EI measures of the BF. Participants were also placed in a supine position, with the right hip and knee joints at 90° of flexion against a horizontal support for PA measurements. PA measurements were recorded at 90°, MidROM, and the EndROM joint positions. US settings were enhanced to improve image quality, including gain (50dB), depth (8cm), and frequency (12MHz). For the IASTM protocol, the BF received 3 sets of 7 strokes in both proximal and distal directions at a treatment angle of 45°. Paired samples t-tests [Time (Pre vs Post)] were used to analyze CSA and EI US data. A two-way repeated measures ANOVA [Joint position (90° vs MidROM vs EndROM) × Time (Pre vs Post)] was used to analyze PA data. An alpha value of P ≤ 0.05 was considered statistically significant for all comparisons. RESULTS: No significant difference was observed across time for CSA (p=0.220) or EI (p=0.515). Additionally, there was no significant joint position × time interaction (p=0.851) for PA. However, a significant main effect (p=0.001) for joint position was observed. Pairwise comparison revealed significant decreases in PA between 90° and MidROM (p=0.038), 90° and EndROM (p=0.001) and MidROM and EndROM (p=0.001). CONCLUSION: Although PA was altered with the corresponding changes in joint position, this was not a result of IASTM. These results indicate that a single bout of IASTM may not evoke architectural change in the hamstrings as measured by ultrasonography.

The effect of dry needling on spasticity, gait and muscle architecture in patients with chronic stroke: A case series study

Objectives The objective of this study was to assess the short-term effects of dry needling on spasticity, gait, and muscle architecture of patients with chronic stroke.Methods A case series study was designed; and six chronic stroke patients with ankle spasticity and gait impairment received a single session of dry needling for gastrocnemius medialis, lateralis, and soleus muscles. The main outcome measures were the Modified Modified Ashworth Scale (MMAS), and Timed Up and Go test (TUG). In addition, ultrasonography measurements (e.g. thickness, pennation angle, and fascicle length) were performed for gastrocnemius medialis at baseline (T0), immediately after intervention (T1) and 30 min after intervention (T2), while the MMAS and TUG Test were only measured at T0 and T2.Results Based on the TUG test, there was a significant improvement in gait function (p = 0.023). Furthermore, the MMAS results (p = 0.014) showed a decrease in resistance to passive movements from plantar flexor muscles. Furthermore, a significant decrease in pennation angle (p = 0.014) and muscle thickness (p = 0.001), and also a significant increase in fascicle length of gastrocnemius medialis (p = 0.001) were observed after dry needling.Discussion & conclusions Based on the outcomes of this study, dry needling application seems to have short term effects in terms of reducing spasticity, improving gait, and muscle architecture of gastrocnemius medialis in patients with chronic stroke. The changes of muscle architecture may be interpreted as the positive effects of dry needling on the physical properties of hypertonic muscles.

Contribution of Neuromuscular Factors to Quadriceps Asymmetry After Anterior Cruciate Ligament Reconstruction.

To quantify quadriceps weakness after anterior cruciate ligament reconstruction (ACLR), researchers have often analyzed only peak torque. However, analyzing other characteristics of the waveform, such as the rate of torque development (RTD), time to peak torque (TTP), and central activation ratio (CAR), can lend insight into the underlying neuromuscular factors that regulate torque development. To determine if interlimb neuromuscular asymmetry was present in patients with ACLR at the time of clearance to return to activity. Cross-sectional study. Laboratory. A total of 10 individuals serving as controls (6 men, 4 women; age = 23.50 ± 3.44 years, height = 1.73 ± 0.09 m, mass = 71.79 ± 9.91 kg) and 67 patients with ACLR (43 men, 24 women; age = 21.34 ± 5.73 years, height = 1.74 ± 0.11 m, mass = 77.85 ± 16.03 kg, time postsurgery = 7.52 ± 1.36 months) participated. Isokinetic (60°/s) and isometric quadriceps strength were measured. Peak torque, TTP, and RTD were calculated across isometric and isokinetic trials, and CAR was calculated from the isometric trials via the superimposed burst. Repeated-measures analyses of variance were used to compare limbs in the ACLR and control groups. No between-limbs differences were detected in the control group ( P > .05). In the ACLR group, the involved limb demonstrated a longer TTP for isokinetic strength ( P = .04; Cohen d effect size [ES] = 0.18; 95% confidence interval [CI] = -0.16, 0.52), lower RTD for isometric ( P < .001; Cohen d ES = 0.73; 95% CI = 0.38, 1.08) and isokinetic ( P < .001; Cohen d ES = 0.84; 95% CI = 0.49, 1.19) strength, lower CAR ( P < .001; Cohen d ES = 0.37; 95% CI = 0.03, 0.71), and lower peak torque for isometric ( P < .001; Cohen d ES = 1.28; 95% CI = 0.91, 1.65) and isokinetic ( P < .001; Cohen d ES = 1.15; 95% CI = 0.78, 1.52) strength. Interlimb asymmetries at return to activity after ACLR appeared to be regulated by several underlying neuromuscular factors. We theorize that interlimb asymmetries in isometric and isokinetic quadriceps strength were associated with changes in muscle architecture. Reduced CAR, TTP, and RTD were also present, indicating a loss of motor-unit recruitment or decrease in firing rate.

Within-and Between-Session Reliability of Ultrasound Imaging Measures in Vastus Lateralis and Gastrocnemius Medialis Muscles

Objective: To determine the within- and between-session reliability of ultrasonography and imaging analysis for measuring muscle architecture of the vastus lateralis (VL) and gastrocnemius medialis (GM) in males who play recreational sport. Methods: Twelve (n=12) males who regularly engage in recreational sport (age: 26.83 ± 4.45 years) participated in this study. Two experimental sessions were conducted 7 days apart. Muscle thickness (MT), pennation angle (Pang) and fascicle length (Lf) for both muscles were determined. Two ultrasound images of the VL were recorded with participants lying supine with the knee at 30o flexion and a further two images were obtained following a 20 min interval. One week later, two images were recorded during the second session. This process was repeated for the GM with participants lying prone with their muscles relaxed and ankle joint in a neutral position (90˚). Results: The within- and between-session minimum detectable changes were: VL MT=0.16 cm, 0.12 cm; VL Pang=0.76˚, 0.99˚; VL Lf=0.84 cm, 0.94 cm; GM MT=0.08 cm, 0.11 cm; GM Pang=0.97˚, 1.45˚; GM Lf=0.36 cm, 0.50 cm, respectively. Other reliability statistics included were intra-class correlation coefficients, coefficient of variation and typical error which also expressed high levels of reliability. Conclusion: The findings of this study suggest that B-mode ultrasonography can be used in confidence by novice radiographers when investigating changes in muscle architecture in males who regularly engage in recreational sport. The reliability statistics reported in this study can be used by researchers for sample size estimation in future studies.

Revisiting the functional anatomy of the palmaris longus as a thenar synergist.

Surgical studies describe the palmaris longus (PL) as a synergist in thumb abduction, which may facilitate its use in restoring thumb function using opponensplasty. However, beyond morphological descriptions and isometric thenar abduction strength measures, the evidence supporting the PL as a thenar synergist in-vivo is limited. The purpose here was to determine whether the PL provides synergistic contributions to thenar musculature by: (1) recording PL muscle activity using indwelling electromyography (EMG) during thumb movements; and (2) quantifying changes in PL muscle architecture using ultrasonography. In 10 healthy males, PL muscle activity was recorded during maximal thenar muscle contractions (abduction, flexion, opposition, adduction, and extension) with the wrist secured in a neutral position. The PL EMG was normalized to its maximal EMG recorded during isometric wrist flexion. Dynamic changes in PL muscle thickness (MT ) were determined during abduction and adduction using ultrasound imaging. The results indicate that the PL is activated during thenar movements with greatest relative PL EMG recorded during thenar abduction (46%), flexion (35%) and opposition (37%). Compared to rest, PL MT significantly increased (21%) during maximal thenar abduction. With direct measures in vivo, this study supports morphological and surgical observations indicating the PL acts as an extrinsic hand muscle in enhancing thenar muscle actions. Knowledge of the synergistic relationship between the PL and thenar musculature may allow for further development of surgical opponensplasty approaches using the abductor pollicis brevis and PL as a functional digastric unit. Clin. Anat. 31:760-770, 2018. © 2017 Wiley Periodicals, Inc.

Equine skeletal muscle adaptations to exercise and training: evidence of differential regulation of autophagosomal and mitochondrial components

BackgroundA single bout of exercise induces changes in gene expression in skeletal muscle. Regular exercise results in an adaptive response involving changes in muscle architecture and biochemistry, and is an effective way to manage and prevent common human diseases such as obesity, cardiovascular disorders and type II diabetes. However, the biomolecular mechanisms underlying such responses still need to be fully elucidated. Here we performed a transcriptome-wide analysis of skeletal muscle tissue in a large cohort of untrained Thoroughbred horses (n = 51) before and after a bout of high-intensity exercise and again after an extended period of training. We hypothesized that regular high-intensity exercise training primes the transcriptome for the demands of high-intensity exercise.ResultsAn extensive set of genes was observed to be significantly differentially regulated in response to a single bout of high-intensity exercise in the untrained cohort (3241 genes) and following multiple bouts of high-intensity exercise training over a six-month period (3405 genes). Approximately one-third of these genes (1025) and several biological processes related to energy metabolism were common to both the exercise and training responses. We then developed a novel network-based computational analysis pipeline to test the hypothesis that these transcriptional changes also influence the contextual molecular interactome and its dynamics in response to exercise and training. The contextual network analysis identified several important hub genes, including the autophagosomal-related gene GABARAPL1, and dynamic functional modules, including those enriched for mitochondrial respiratory chain complexes I and V, that were differentially regulated and had their putative interactions ‘re-wired’ in the exercise and/or training responses.ConclusionHere we have generated for the first time, a comprehensive set of genes that are differentially expressed in Thoroughbred skeletal muscle in response to both exercise and training. These data indicate that consecutive bouts of high-intensity exercise result in a priming of the skeletal muscle transcriptome for the demands of the next exercise bout. Furthermore, this may also lead to an extensive ‘re-wiring’ of the molecular interactome in both exercise and training and include key genes and functional modules related to autophagy and the mitochondrion.

Structural and functional anatomy of the palmaris brevis: grasping for answers.

The palmaris brevis (PB) is a small cutaneous hand muscle that has been described as the most mysterious muscle from a functional and developmental perspective [Kaplan () Kaplan's Functional and Surgical Anatomy of the Hand]. Functionally, the PB is considered to deepen the hollow of the palm and to protect the neurovasculature of the ulnar canal. Although the function of the PB has been inferred from cadaveric observations, the electromyographic (EMG) activity of this muscle has not been explored systematically during specific movements of the hand. The purpose of this study was to record PB intramuscular EMG activity during dynamic grasping tasks, and to quantify the change in PB muscle length (ML ) and thickness (MT ) incurred during maximal contraction using ultrasound imaging. Intramuscular EMG was recorded from the PB in the dominant hands of 12 healthy participants (11 males, one female; age: 27 ± 4 years) during maximal abduction, flexion and opposition of the 5th digit, and two grasping tasks. Abduction of the 5th digit yielded the greatest EMG activity in most individuals (seven out of 11), and produced significantly less PB EMG activity when compared with grasping a cylindrical-shaped object (P = 0.003) but not a spherical-shaped object (P=0.130). During maximal abduction of the 5th digit, PB ML decreased in both the left (28±11%; P=0.002) and right (32±5%; P=0.002) hands. Similarly, a concomitant increase in PB MT was observed in the left (68±30%; P=0.002) and right (85±44%; P=0.002) hands during the same contraction. These EMG results indicate that the PB is voluntarily activated during prehensile and non-prehensile movements of the hand with significant changes in muscle architecture. The study supports the preservation of the PB in surgical procedures based on its proposed protective role as a muscular barrier to the neurovasculature within the ulnar canal.

Physiological and Biomechanical Responses to Prolonged Heavy Load Carriage During Level Treadmill Walking in Females.

Heavy load carriage has been identified as a main contributing factor to the high incidence of overuse injuries in soldiers. Peak vertical ground reaction force (VGRFMAX) and maximal vertical loading rates (VLRMAX) may increase during heavy prolonged load carriage with the development of muscular fatigue and reduced shock attenuation capabilities. The objectives of the current study were (1)to examine physiological and biomechanical changes that occur during a prolonged heavy load carriage task, and (2)to examine if this task induces neuromuscular fatigue and changes in muscle architecture. Eight inexperienced female participants walked on an instrumented treadmill carrying operational loads for 60minutes at 5.4km·h-1. Oxygen consumption ( V ˙ O 2 ), heart rate, rating of perceived exertion (RPE), trunk lean angle, and ground reaction forces were recorded continuously during task. Maximal force and in-vivo muscle architecture were assessed pre- and posttask. Significant increases were observed for VGRFMAX, VLRMAX, trunk lean angle, [Formula: see text], heart rate, and RPE during the task. Increased vastus lateralis fascicle length and decreased maximal force production were also observed posttask. Prolonged heavy load carriage, in an inexperienced population carrying operational loads, results in progressive increases in ground reaction force parameters that have been associated with overuse injury.

Changes in three-dimensional muscle structure of rabbit gastrocnemius, flexor digitorum longus, and tibialis anterior during growth

Muscular contraction dynamics depends on active and passive muscle properties (e.g., the force-velocity relation) as well as on the three-dimensional (3D) muscle structure (e.g., the muscle fascicle architecture and aponeurosis dimensions). Much is known about active muscle force generation and the muscle architecture at a particular age (mostly for adult specimens), but less is known about changes in muscle structure during growth. The present study analyzed growth-related changes in the muscle structure of rabbit gastrocnemius lateralis (GL), gastrocnemius medialis (GM), flexor digitorum longus (FDL), and tibialis anterior (TA). Changes in tendon length, muscle belly dimensions (length, width, thickness), as well as aponeurosis length, width, and area were determined using 55 rabbits between 18 and 108 days old. Additionally, the 3D muscle fascicle architecture of five rabbits of different ages (21, 37, 50, 70, 100 days) was determined using a manual digitizer.We found an almost linear increase over time in most of the geometrical parameters observed. GL and GM showed very similar growth characteristics. In contrast to the pronounced increase in muscle belly length of GL and GM, FDL and TA exhibited more uniform muscle belly growth in length, width, and thickness. In general, the aponeuroses of the muscles exhibited lower growth rates in width than in length, and aponeurosis areas were larger than physiological cross-sectional areas. There were almost no changes in fascicle lengths with increasing age for GL, GM, and FDL. In contrast, there was a clear increase in TA fascicle length from about 20 to over 40mm. Pennation angles of TA (11.0 ± 2.1°) and FDL (16.7 ± 3.2°) remained almost unchanged but increased for GL from 13.4 ± 3.3° to 24.3 ± 6.5° from the youngest to the oldest animal. For all muscles observed, the tendon-muscle fascicle length ratio (rTFL) changed during growth. GL and GM exhibited similar increases in rTFL from about 4–8. FDL showed the highest ratio, which increased from about 8–13, whereas TA had the lowest ratio, which decreased slightly from 2 to 1.5.The outcomes demonstrate new findings regarding changes in 3D muscle architecture and aponeurosis shape during growth, and they provide information for muscle force generation, functional relevance, and adaptation with respect to animal age. Therefore, the results help to improve understanding of muscle growth processes and can be used as input data for muscle growth modeling.

MEDIAL GASTROCNEMIUS MUSCLE ARCHITECTURE AND PLANTIFLEXORS TORQUE IN COMMUNITY OLDER WOMEN

AbstractThe aging process can lead to changes in muscle architecture, such as reduction of muscle thickness (MT), pennation angle (PA) and fascicle length (FL), which may contribute to dinapenia. Thus, the aim of the study was to correlate the medial gastrocnemius (MG) muscle architecture and plantiflexors peak of torque (PT) of community older women. Cross-sectional study approved by the Research Ethics Committee of Federal University of Parana (36003814.2.0000.0102). The study included 48 older women (70.4 ± 5.1 years-old; BMI: 27.8 ± 4 Kg/m). MG architecture was evaluated at 30% of the distance between medial tibia condyle and medial malleolus, using a B-mode ultrasonography imaging device (Logiq Book-XP, General Eletric®) with a linear-array probe (50mm, 4cm of depth, 11 MHz). The ImageJ software was used to analyze MT (mean distance between deep and superficial aponeuroses), PA (angle of insertion of muscle fiber fascicles into the deep aponeurosis) and FL (fascicle length between the superior and deep aponeuroses). The concentric plantiflexors PT was evaluated by an isokinetic dynamometer (System4, Biodex®) with 30° of range of motion, three repetitions each set performed at 60°/s and 180°/s. To verify the association between variables the Pearson correlation test was used (p<0.05). The mean±SD were: MT=1.6 ± 0.2cm; PA=26.7 ± 3.4°; FL=3.8 ± 0.5cm; PT60°/s=39.8 ± 11.4Nm; PT180°/s 31 ± 9.2Nm. It was observed correlation between MT and PT60°/s (r=0.412, p=0.004); MT and PT180°/s (r=0.387, p=0.007); FL and PT60°/s (r=0.334, p=0.020). It can be concluded that the greater MG thickness and FL, the greater is the plantiflexors power and strength of community older women.

Bilateral differences in muscle fascicle architecture are not related to the preferred leg in jumping athletes.

In many sports, athletes have a preferred leg for sport-specific tasks, such as jumping, which leads to strength differences between both legs, yet the underlying changes in force-generating mechanical properties of the muscle remain unknown. The purpose of this study was to investigate whether the muscle architecture of the medial gastrocnemius (MG) is different between both legs in well-trained jumping athletes and untrained individuals. In addition, we investigated the effect of two ankle joint positions on ultrasound muscle architecture measurements. Muscle architecture of both legs was measured in 16 athletes and 11 untrained individuals at two ankle joint angles: one with the ankle joint in a tendon slack length (TSL) angle and one in a 90° angle. Fascicle lengths and pennation angles at TSL were not different between the preferred and non-preferred legs in either group. The comparison between groups showed no difference in fascicle length, but greater pennation angles were found in the athletes (21.7°±0.5°) compared to the untrained individuals (19.8°±0.6°). Analyses of the muscle architecture at a 90° angle yielded different results, mainly in the comparison between groups. These results provide only partial support for the notion of training-induced changes in muscle architecture as only differences in pennation angles were found between athletes and untrained individuals. Furthermore, our results provide support to the recommendation to take into account the tension-length relationship and to measure muscle architecture at individually determined tendon slack joint angles.

Thigh Muscle Architecture Changes During a Soccer Season in Previously Injured and Non-injured Female Athletes

Thigh Muscle Architecture Changes During a Soccer Season in Previously Injured and Non-injured Female Athletes